1,162 research outputs found
On the Correlated X-ray and Optical Evolution of SS Cygni
We have analyzed the variability and spectral evolution of the prototype
dwarf nova system SS Cygni using RXTE data and AAVSO observations. A series of
pointed RXTE/PCA observations allow us to trace the evolution of the X-ray
spectrum of SS Cygni in unprecedented detail, while 6 years of optical AAVSO
and RXTE/ASM light curves show long-term patterns. Employing a technique in
which we stack the X-ray flux over multiple outbursts, phased according to the
optical light curve, we investigate the outburst morphology. We find that the
3-12 keV X-ray flux is suppressed during optical outbursts, a behavior seen
previously, but only in a handful of cycles. The several outbursts of SS Cygni
observed with the more sensitive RXTE/PCA also show a depression of the X-rays
during optical outburst. We quantify the time lags between the optical and
X-ray outbursts, and the timescales of the X-ray recovery from outburst. The
optical light curve of SS Cygni exhibits brief anomalous outbursts. During
these events the hard X-rays and optical flux increase together. The long-term
data suggest that the X-rays decline between outburst. Our results are in
general agreement with modified disk instability models (DIM), which invoke a
two-component accretion flow consisting of a cool optically thick accretion
disk truncated at an inner radius, and a quasi-spherical hot corona-like flow
extending to the surface of the white dwarf. We discuss our results in the
framework of one such model, involving the evaporation of the inner part of the
optically thick accretion disk, proposed by Meyer & Meyer-Hofmeister (1994).Comment: 24 pages, 8 figures, 2 tables, accepted for publication in Ap
Sperm Reserves and its Relationship to Parameters of the Testis, Epididymis and Vas Deferens of Local Cocks in the Sahel Region of Nigeria
ABSTRACT The morphometry and sperm reserves of the testis, epididymis and vas deferens of 19 sexually active adult local cocks were studied. The average live weight of the cocks was 1.879±0.316 kg and that of the paired testis, epididymis, vas deferens were 12.17±4.75 g, 0.52±0.19 g and 1.36±0.56 g, respectively. The length of the testis, epididymis and vas deferens were 3.42±0.50 cm, 1.91±0.38 cm and 11.5±1.34 cm, respectively. In majority of cases, the parameters of the left organs were insignificantly greater than those of the right. The width, thickness, circumference and volume of the testis as well as the diameter and volume of the epididymis and vas deferens were recorded. There were strong positive correlation between the weight of the testis and epididymis (r=±0.82) or vas deferens (r=±0.66). The gonadal sperm reserve was 2.11±1.11 x 10 9 sperm (173.7±71.5 x 10 6 sperm g -1 ) and the extrangonadal sperm, 1.77x 10 9 sperm. The vas deferens with 89.8% of the extragonadal sperm reserved as the main storage organ of sperm for use during threading. Sperm reserve was positively correlated to body weight (r=±0.77, P = 0.000) and to the length of the testis (r=±0.55, P = 0.015). This may suggest that body weight and testicular length are indicators of fertility. The high gonadal sperm and hence reproductive potential may reflect an adaptive change in the local cocks, which have a very high mating frequency per day
ORFEUS II and IUE Spectroscopy of EX Hydrae
Using ORFEUS-SPAS II FUV spectra, IUE UV spectra, and archival EUVE deep
survey photometry, we present a detailed picture of the behavior of the
magnetic cataclysmic variable EX Hydrae. Like HUT spectra of this source, the
FUV and UV spectra reveal broad emission lines of He II, C II-IV, N III and V,
O VI, Si III-IV, and Al III superposed on a continuum which is blue in the UV
and nearly flat in the FUV. Like ORFEUS spectra of AM Her, the O VI doublet is
resolved into broad and narrow emission components. Consistent with its
behavior in the optical, the FUV and UV continuum flux densities, the FUV and
UV broad emission line fluxes, and the radial velocity of the O VI broad
emission component all vary on the spin phase of the white dwarf, with the
maximum of the FUV and UV continuum and broad emission line flux light curves
coincident with maximum blueshift of the broad O VI emission component. On the
binary phase, the broad dip in the EUV light curve is accompanied by strong
eclipses of the UV emission lines and by variations in both the flux and radial
velocity of the O VI narrow emission component. The available data are
consistent with the accretion funnel being the source of the FUV and UV
continuum and the O VI broad emission component, and the white dwarf being the
source of the O VI narrow emission component.Comment: 21 pages, 10 Postscript figures; LaTeX format, uses aaspp4.sty;
table2.tex included separately because it must be printed sideways - see
instructions in the file; accepted on 1999 Feb 20 for publication in The
Astrophysical Journa
Effect of selenium supplementation on adiponectin concentration as a marker of type-2 diabetes risk in UK pregnant women
Disk Diffusion Propagation Model for the Outburst of XTE J1118+480
We present a linear diffusion model for the evolution of the double-peaked
outburst in the transient source XTEJ1118+480. The model treats the two
outbursts as episodic mass deposition at the outer radius of the disk followed
by evolution of disk structure according to a diffusion process. We demonstrate
that light curves with fast-rise, exponential decay profile are a general
consequence of the diffusion process. Deconvolution of the light curve proves
to be feasible and gives an input function specifying mass deposition at the
outer disk edge as well as the total mass of the disk, both as functions of
time. The derived evolution of total disk mass can be correlated with the
observed evolution of the ~0.1 Hz QPO in the source reported in Wood et al.
(2000).Comment: 26 pages, 6 figures, accepted for publication in Ap
Therapeutic potential of transdermal glyceryl trinitrate in the management of acute stroke
The nitric oxide donor, glyceryl trinitrate (GTN), is a candidate treatment for the management of acute stroke with haemodynamic and potential reperfusion and neuroprotective effects. When administered as a transdermal patch during the acute and subacute phases after stroke, GTN was safe, lowered blood pressure, maintained cerebral blood flow, and did not induce cerebral steal or alter functional outcome. However, when given within 6 h of stroke onset, GTN reduced death and dependency (odds ratio 0.52; 95% confidence interval 0.34â0.78), death, disability, cognitive impairment and mood disturbance, and improved quality of life (data from two trials, n = 312). In a pooled analysis of four studies (n = 186), GTN reduced between-visit systolic blood pressure variability over days 1â7 compared with no GTN (mean difference -2.09; 95% confidence interval -3.83 to -0.35; p = 0.019). The efficacy of GTN given in the ultra-acute/pre-hospital setting is currently being assessed and, if found to be beneficial, the implications for hyperacute stroke practice are significant. Here, we discuss the evidence to date, potential mechanisms of action and future possibilities, including unanswered questions, for the therapeutic potential of GTN in acute stroke
When does the action start and finish? Making the case for an ethnographic action research in educational research
This paper explores how ethnographic and action research methodologies can be justifiably combined to create a new methodological approach in educational research. It draws on existing examples in both educational research and
development studies that have discussed the use of ethnography and action research in specific projects. Interpretations of ethnography and action research
are developed that aim to minimise the epistemological differences between them.
The paper also contextualises an âethnographic action researchâ approach with reference to an example of the authorâs research into participation in three âreceptionâ (first year of schooling) classes in the United Kingdom. It is argued that research into the theme of participation in early years education, using participative methods, was particularly suitable for this new methodological
approach
The Virtual International Stroke Trials Archive
BACKGROUND AND PURPOSE: Stroke has global importance and it causes an increasing amount of human suffering and economic burden, but its management is far from optimal. The unsuccessful outcome of several research programs highlights the need for reliable data on which to plan future clinical trials. The Virtual International Stroke Trials Archive aims to aid the planning of clinical trials by collating and providing access to a rich resource of patient data to perform exploratory analyses.
METHODS: Data were contributed by the principal investigators of numerous trials from the past 16 years. These data have been centrally collated and are available for anonymized analysis and hypothesis testing.
RESULTS: Currently, the Virtual International Stroke Trials Archive contains 21 trials. There are data on \u3e15,000 patients with both ischemic and hemorrhagic stroke. Ages range between 18 and 103 years, with a mean age of 69+/-12 years. Outcome measures include the Barthel Index, Scandinavian Stroke Scale, National Institutes of Health Stroke Scale, Orgogozo Scale, and modified Rankin Scale. Medical history and onset-to-treatment time are readily available, and computed tomography lesion data are available for selected trials.
CONCLUSIONS: This resource has the potential to influence clinical trial design and implementation through data analyses that inform planning
The early X-ray emission from V382 Velorum (=Nova Vel 1999): An internal shock model
We present the results of ASCA and RXTE observations of the early X-ray
emission from the classical nova V382 Velorum. Its ASCA spectrum was hard
(kT~10 keV) with a strong (10**23 cm**-2) intrinsic absorption. In the
subsequent RXTE data, the spectra became softer both due to a declining
temperature and a diminishing column. We argue that this places the X-ray
emission interior to the outermost ejecta produced by V382 Vel in 1999, and
therefore must have been the result of a shock internal to the nova ejecta. The
weakness of the Fe K alpha lines probably indicates that the X-ray emitting
plasmas are not in ionization equilibrium.Comment: 16 pages (including 4 figures), accepted for publication in Ap
General-relativistic constraints on the equation of state of dense matter implied by kilohertz quasi-periodic oscillations in neutron-star X-ray binaries
If the observed millisecond variability in the X-ray flux of several
neutron-star low-mass X-ray binaries (LMXBs) is interpreted within a
general-relativistic framework (Kluzniak, Michelson \& Wagoner 1990) extant at
the time of discovery, severe constraints can be placed on the equation of
state (e.o.s.) of matter at supranuclear densities. The reported maximum
frequency (1.14 +- 0.01 kHz) of quasiperiodic oscillations observed in sources
as diverse as Sco X-1 and 4U 1728-34 would imply that the neutron star masses
in these LMXBs are M > 1.9 M_solar, and hence many equations of state would be
excluded. Among the very few still viable equations of state are the e.o.s. of
Phandaripande and Smith (1975), and e.o.s. AV14 + UVII of Wiringa, Fiks \&
Fabrocini (1988).Comment: The figures can be found in the references cited in the captions. A
longer version of this paper was submitted to a refereed journal on January
6, 1997 (345 days ago
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